That's a fluke.

That's a fluke.
“That’s a fluke”指的是某事的成功纯属偶然,而非因为技能或努力。这个短语常用于描述意外的好运,比如不小心打进的球或者毫无计划下的成功。
Believe it or not, winning the lottery was a fluke.
信不信由你,赢得彩票完全是偶然的。
That goal he scored was totally a fluke.
他进的那个球完全是侥幸。
No one expected him to win, his victory was just a fluke.
没有人预料他会赢,他的胜利只是个意外。